Heart development involves the generation and interaction of diverse cell types to form a functional organ. Myocytes, endocardium, fibroblasts, epicardium, vascular endothelium and smooth muscle are the primary cell types that comprise the heart. The pro-epicardial organ is the source of many of these cells. It is a transitory embryonic structure whose progeny form, amongst other structures, the epicardium and intracardiac arteries including the coronary arteries.. Thus, an understanding of the role of the pro-epicardial organ and its progeny is essential for an understanding of heart development. We have isolated novel protein, Bves, that is expressed in most, if not cells of the pro-epicardial organ, migrating epicardial, delaminated freely migratory mesenchyme and coronary vascular smooth muscle cells. In addition, the subcellular localization of Bves undergoes a dramatic change with differentiation of this cell lineage. Our current data suggests that Bves is a protein that may play a role in cell adhesion during coronary vessel development. Our aims are to determine whether Bves is an integrated membrane (Aim ), to identify domains that regulate Bves function in vitro and during organogenesis (Aim 2) and to determine how loss of Bves function potentially alters morphogenesis (Aim 3). Taken together these aims will determine the function(s) of Bves, its role in the generation of coronary vessels and basic insight into coronary vessel biology.